U.S. patent number 10,473,304 [Application Number 16/063,453] was granted by the patent office on 2019-11-12 for reducing thermal sensitivity of a lighting arrangement.
This patent grant is currently assigned to LUMILEDS LLC. The grantee listed for this patent is Lumileds LLC. Invention is credited to Juergen Mertens, Florent Monestier, Benno Spinger.
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United States Patent |
10,473,304 |
Spinger , et al. |
November 12, 2019 |
Reducing thermal sensitivity of a lighting arrangement
Abstract
The invention relates to a lighting arrangement with at least
one LED lighting element (15) arranged on a support member (12). An
optical element (16) is arranged spaced from the LED lighting
element (15) in a first direction O. A holder (14) is provided to
hold the optical element (16) in a position relative to the LED
lighting element (15). The holder (14) comprises at least a first
holding portion (24a) extending from the support member (12) into
the first direction O and a second holding portion (24b) connected
to the optical element (16). The second holding portion (24b) is
arranged such that at least a part extends into the first direction
O. The second holding portion (26b) is spaced from the first
holding portion (24a) in a direction traverse to the first
direction O. In the case of distortions due to temperature changes
and a mismatch of the coefficient of thermal expansion, the
lighting arrangement minimizes variations in the displacement of
the optical element (16) relative to the LED lighting element
(15).
Inventors: |
Spinger; Benno (Aachen,
DE), Monestier; Florent (Aachen, DE),
Mertens; Juergen (Aachen, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Lumileds LLC |
San Jose |
CA |
US |
|
|
Assignee: |
LUMILEDS LLC (San Jose,
CA)
|
Family
ID: |
57123842 |
Appl.
No.: |
16/063,453 |
Filed: |
September 27, 2017 |
PCT
Filed: |
September 27, 2017 |
PCT No.: |
PCT/EP2017/074532 |
371(c)(1),(2),(4) Date: |
June 18, 2018 |
PCT
Pub. No.: |
WO2018/065278 |
PCT
Pub. Date: |
April 12, 2018 |
Foreign Application Priority Data
|
|
|
|
|
Oct 4, 2016 [EP] |
|
|
16192238 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01S
5/02288 (20130101); G02B 7/028 (20130101); G02B
7/008 (20130101); F21V 14/006 (20130101); F21S
41/29 (20180101); F21V 5/007 (20130101); F21V
19/0015 (20130101); F21S 41/143 (20180101); F21S
41/153 (20180101); F21V 17/10 (20130101); F21S
41/663 (20180101); F21Y 2105/10 (20160801); F21Y
2115/10 (20160801) |
Current International
Class: |
F21V
3/00 (20150101); F21V 5/00 (20180101); F21V
14/00 (20180101); H01S 5/022 (20060101); F21V
19/00 (20060101); G02B 7/02 (20060101) |
Field of
Search: |
;362/249.02-249.04,249.07-249.11,311.02,433-456 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
102008047277 |
|
Apr 2010 |
|
DE |
|
0454174 |
|
Oct 1991 |
|
EP |
|
2306077 |
|
Apr 2011 |
|
EP |
|
2884157 |
|
Jun 2015 |
|
EP |
|
2003-185904 |
|
Jul 2003 |
|
JP |
|
Primary Examiner: Han; Jason M
Attorney, Agent or Firm: Volpe and Koenig, P.C.
Claims
The invention claimed is:
1. A lighting arrangement comprising: at least one light emitting
diode (LED) lighting element arranged on a support member; an
optical element arranged spaced from the LED lighting element in a
first direction; and a holder to hold the optical element in a
position relative to the LED lighting element, the holder
comprising at least a first holding portion extending from the
support member into the first direction and a second holding
portion connected to the optical element arranged such that at
least a part of the second holding portion extends into the first
direction, wherein the second holding portion is spaced from the
first holding portion in a direction traverse to the first
direction, wherein the first holding portion and the second holding
portion are connected by a first connecting portion arranged to
form an angle with both the first holding portion and the second
holding portion, wherein the first connecting portion is a plane
wall element having a greater thickness than the first holding
portion and the second holding portion, and wherein the optical
element is one piece with the first holding portion and the second
holding portion.
2. The lighting arrangement of claim 1, wherein the first holding
portion extends into the first direction beyond the optical
element.
3. The lighting arrangement of claim 1, wherein the first holding
portion and the second holding portion are substantially parallel
to each other.
4. The lighting arrangement of claim 1, wherein the first
connecting portion extends substantially perpendicular to the first
direction.
5. The lighting arrangement of claim 1, wherein the second holding
portion is connected to the optical element by a second connecting
portion extending substantially perpendicular to the first
direction.
6. The lighting arrangement of claim 1, further comprising: a
plurality of LED lighting elements arranged on the support member
spaced apart from each other; and a plurality of optical elements
arranged spaced apart from the plurality of LED lighting elements
in the first direction, wherein the plurality of optical elements
are connected to each other.
7. The lighting arrangement of claim 1, wherein the first holding
portion and the second holding portion are plane wall elements.
8. The lighting arrangement of claim 1, wherein the first holding
portion and the second holding portion surround the optical
element.
9. The lighting arrangement of claim 1, wherein the holder is a box
shaped housing comprising at least a pair of first housing walls
parallel to each other and a pair of second housing walls parallel
to each other, first housing walls and the second housing walls
substantially perpendicular to each other.
10. The lighting arrangement of claim 1, wherein the holder element
comprises a base portion and a clamp element affixing the base
portion to the support member.
11. The lighting arrangement of claim 1, wherein the optical
element comprises one or more of a collimator element and a lens
element.
Description
FIELD OF THE INVENTION
The invention relates to the field of lighting, and more
specifically to a lighting arrangement comprising at least one LED
lighting element and an optical element.
BACKGROUND OF THE INVENTION
Lighting arrangements with LEDs are used for an ever increasing
number of lighting applications. In many cases, an optical element
is arranged in front of an LED to alter the light emission, such as
e.g. a lens, a reflector and/or a collimator to obtain an emitted
light beam of desired properties.
The properties of the emitted light may depend on the exact
positioning of the optical element relative to the LED. An exact
positioning of the optical element is therefore advantageous.
DE 10 2008 047 277 A1 shows a device having a carrier arrangement
holding an objective to change a focal plane relative to a charge
coupled device chip. The objective is arranged in a section of a
compensation body that extends along an optical axis, wherein the
compensation body is connected in another section with the carrier
arrangement. The compensation body includes a material with a
thermal expansion coefficient, which is measured such that a
temperature-dependent change of the arrangement of the focal plane
to the optical component is balanced.
U.S. Pat. No. 5,270,870 A discloses an athermalized beam source and
collimator assembly includes a collimator lens spaced from a
circular foldback flexure plate by a lens barrel. The circular
foldback flexure plate incorporates a circular foldback flexure
adjacent the beam source mount to isolate the beam source from the
ambient environment and to athermalize the assembly. The beam
source mount and circular foldback flexure plate are composed of a
material that is identical in composition and CTE as the portion of
the beam source that is attached to the beam source mount.
EP 2 884 157 A2 shows a motor vehicle headlamp with at least one
semiconductor light source and a primary optical system which
collects light emitted from the semiconductor light source and is
directed to a secondary optical system, wherein the primary optical
system receives the light from the light source via a light entry
surface and the light is emitted out via a light exit surface,
wherein the primary optical system has a connecting flange with
which the primary optical system is kept in a holder in at least
two fixed bearings, wherein a first section of the connecting
flange is curved like a dome.
SUMMARY OF THE INVENTION
It may be considered an object to achieve stable positioning of an
optical element over a wide range of operating conditions.
This may be achieved by a lighting arrangement according to claim
1. Dependent claims refer to preferred embodiments.
The present inventors have considered that thermal changes, e.g.
due to a change in ambient temperature or due to LED electrical
operating power dissipated as heat, may significantly influence a
holding structure provided to mount an optical element relative to
an LED. In particular, if the structure supporting the LED and the
optical element is comprised of different parts or different
materials with a differing coefficient of thermal expansion (CTE),
the structure may undergo distortions with increasing temperature
that could lead to variations in the relative arrangement of the
LED and the optical element. In order to improve the thermal
stability of the positioning of the optical element, the inventors
have proposed a special structure which has proven to have
relatively low temperature sensitivity even for significant CTE
mismatch.
The lighting arrangement according to the invention comprises at
least one LED lighting element. The term LED lighting element
should be understood to comprise any type of solid state lighting
element, such as e.g. light emitting diodes, organic light emitting
diodes, laser diodes, etc. An LED lighting element may comprise a
single one or a plurality of several of such solid state lighting
elements, e.g. one or a plurality of light emitting diodes arranged
in close proximity.
One or several of such LED lighting elements may be arranged on a
support member, and at least one optical element may be arranged
spaced from the LED lighting element in a first direction, e.g.
along an optical axis. Preferably, the optical element may be
arranged directly in front of the LED lighting element,
particularly preferred in the main light emission direction, e.g.
perpendicular to a light emitting surface of the LED lighting
element.
The optical element may be any type of element with an optical
function, in particular to alter the beam of light emitted from the
LED lighting element. The optical element may thus comprise or be
comprised of a reflector, a collimator, a lens, an optical filter,
a baffle, etc, or a combination of such elements. Preferably, it is
made of or at least comprises a transparent or translucent
material. The optical element preferably receives light from the
LED lighting element and emits a modified beam, which may be e.g.
focussed, collimated, redirected, filtered etc.
A holder is provided to hold the optical element in a position
relative to the LED lighting element. The holder according to the
invention has a specially designed structure, such that it
comprises at least a first and a second holding portion. The first
holding portion extends from the support member into the first
direction and the second holding portion, which is connected
directly or indirectly to the optical element, is arranged such
that at least a part of it also extends into the first direction.
The second holding portion is spaced from the first holding portion
in a traverse direction, e. g. perpendicular to the first
direction.
The holder proposed for the lighting arrangement according to the
invention has a structure designed to be able to achieve stable
positioning of the optical element even in cases of severe CTE
mismatch, e.g. between the support member and the holder. The first
and second holding portions are not aligned, but offset in the
traverse direction, thus being able to e.g. form a loop-like
structure. A section of the holder in the shape of a loop may act
as a spring, i.e. deform. In cases of severe CTE mismatch, the
position of the optical element relative to the first direction,
e.g. the optical axis, can remain relatively stable, because
thermal expansion can be at least partly compensated in the first
direction by the first and second holding portions.
According to preferred embodiments, the first holding portion may
extend into the first direction beyond the optical element. The
second holding portion may then extend from its connection to the
optical element also into the first direction. Thus, a loop may be
formed.
As explained above, at least a part of the second holding portion
extends into the first direction. This should be understood to
cover also inclined arrangements, where e.g. the second holding
portion forms an angle of, for example, 25-65.degree. to the first
direction. Also, this comprises non-angular, e.g. bent or rounded
shapes of the second holding portion, as long as they at least
partially extend into the first direction. However, it is preferred
to provide the first and/or the second holding portions to extend
at least substantially straight. In particular, it is preferred
that the first and second holding portions may be arranged at least
substantially in parallel to each other. The term "at least
substantially" should be understood to cover minor variations, such
as e.g. +/-15.degree. or less, preferably +/-5.degree. or less.
According to one aspect of the invention, the first and second
holding portions are connected by a first connection portion and
the first connection portion is arranged to form an angle with both
the first and second holding portions. The angle may be e.g.
greater than 30.degree., preferably greater than 60.degree.. In a
particularly preferred embodiment, the first and second holding
portions are arranged at least substantially at right angles to the
first connecting portion.
The second holding portion may be directly attached to the optical
element, or the connection may be indirect through one or more
intervening elements. In a preferred embodiment, the second holding
portion may be connected to the optical element by a second
connecting portion. The second connecting portion may extend at
least substantially perpendicular (i.e. 90.degree.+/-15.degree.,
preferably 90.degree.+/-5.degree.) to the first direction.
The holder may comprise one or more further holding portions
besides the first and second holding portions. In some embodiments,
the further holding portions may extend into the first direction
and be arranged at least substantially in parallel to each other
and to the first and second holding portions. The holding portions
may be interconnected by connecting portions, which may be arranged
perpendicularly. In one embodiment, the lengths of the holding
portions differ. Shorter holding portions may be arranged closer to
the optical element. The holding portions may be arranged such that
each is shorter than the holding portion next to it into the
direction away from the optical element.
While the lighting arrangement may offer great advantages already
for a single LED lighting element and corresponding optical
element, it is particularly preferred to provide a plurality of LED
lighting elements and corresponding optical elements arranged
relative thereto. In particular, a plurality of LED lighting
elements may be arranged on the same support member spaced from
each other, e. g. in a line or matrix. The optical elements may be
arranged spaced from the LED lighting elements in the same
direction. In particular, the optical elements may be connected to
each other. The holder may be provided to hold two or more,
preferably all of the optical elements in a position relative to
the support member to thus ensure exact positioning for all optical
elements.
The holder may have many different shapes. Its main function is to
define the position of the optical element relative to the support
member, i.e. to lock its displacement. Any type, shape or
construction of a holder which serves this function, i.e. locks the
position of the optical element with respect to at least one,
preferably two, further preferably all three of x, y, and z
directions may be used.
In preferred embodiments, the holder may be comprised e.g. of a
plurality of bars, beams or other structures. Preferably, at least
the first and second holding portions may be provided as plane wall
elements. The holder may be comprised of a plurality of such plane
wall elements. The first connecting portion is provided as a plane
wall element having a greater thickness than the first and second
holding portions.
In a preferred embodiment, the first and second holding portions
may be arranged to surround the optical element. Thus, at least a
portion of the holder may be arranged as a housing surrounding the
optical element. In particular, the holder may be a box-shaped
housing with at least a pair of first housing walls arranged in
parallel to each other and a pair of second housing walls arranged
in parallel to each other. The first and second housing walls are
preferably arranged at least substantially perpendicular to each
other.
In a further preferred embodiment, the holder may comprise a base
portion, which is e.g. in contact with the support member. A clamp
element may be arranged to fix the base portion to the support
member. The holder may comprise a flange for engagement with the
clamp element.
It is particularly preferred to provide the first and second
holding portions of the holder in one piece, e.g. manufactured
together in injection moulding. According to one aspect of the
invention, the optical element is provided as one piece with both
the first and second holding portions, as well as optionally and
preferably any connection portions. A holder with an optical
element provided in one piece is particularly simple and efficient
to manufacture.
These and other aspects of the invention will be apparent from and
elucidated with reference to the embodiments described
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 shows a perspective view of a first embodiment of a lighting
arrangement;
FIG. 2, 3 show a side view and a top view of the lighting
arrangement of FIG. 1;
FIG. 4 shows a longitudinal sectional view along B . . . B in FIG.
3;
FIG. 5 shows a cross-sectional view along A . . . A in FIG. 2;
FIG. 6 shows an enlarged view of the portion C in FIG. 5;
FIG. 7 shows a partial cross-sectional view of a second embodiment
of a lighting arrangement;
FIG. 8 shows a partial cross-sectional view of a third embodiment
of a lighting arrangement;
FIG. 9a, 9b schematically show the structure of a holder according
to a generic embodiment;
FIG. 10a, 10b show the structure of a holder according to a
comparative example,
FIG. 11 shows a partial cross-sectional view of a fourth embodiment
of a lighting arrangement.
DETAILED DESCRIPTION OF EMBODIMENTS
A first embodiment of a lighting arrangement 10 shown in FIG. 1-3
comprises a support member, in the present example a base plate 12,
onto which a plurality of light emitting diodes 15 see (FIG. 6--not
visible in FIGS. 1-5) and a holder 14 for a number of optical
elements 16 are mounted. As the skilled person will understand, the
base plate 12 shown is a simple an example of a support member
suited for illustration of the holding function of the optical
elements 16 relative to the base plate 12. In actual embodiments,
the base plate 12 may e.g. be a circuit board. In more detailed
embodiments, further components, not shown in the figures, may be
arranged on the base plate 12, such as e.g. electronic components,
conductor tracks, thermal interface elements and/or one or more
heat sinks.
As shown, the holder 14 is box-shaped to surround the optical
elements 16. It has a surrounding flange 22, which is held down by
a clamp 18 which may be fixed to the base plate 12 e.g. by a screw
connection.
FIGS. 4-6 show sectional views of the lighting arrangement 10. As
shown in the enlarged view of FIG. 6, LEDs 15 are arranged on the
base plate 12. Spaced by a small distance d in the direction of an
optical axis O, the optical elements 16 are positioned. A plurality
of LED elements 15 are arranged in a line on top of the base plate
12. As shown in FIG. 4, the optical elements 16 are each arranged
in front of the individual LED elements 15.
Each optical element 16 comprises a TIR collimator portion 16a
arranged towards the LED elements 15 for receiving light therefrom
and a lens portion 16b to emit the light as a shaped illumination
beam into the direction of the optical axis O. In the example
shown, the holder 14 is manufactured in one piece with the optical
elements 16, made from a transparent material e.g. silicone.
The LED elements 15 of the lighting arrangement 10 form an LED
matrix, which may be e.g. used in automotive front lighting. In
particular, the lighting arrangement 10 may be used for adaptive
driving lighting, where the LEDs may be operated independently or
in segments in order adjust the beam to a specific driving
situation. As shown in the figures, in particular FIGS. 4-6, the
optical elements 16 are each arranged in front of the LED elements
15. Distance d is preferably very small to allow good coupling of
light from the LED element 15 into the TIR collimator portion 16a
of each optical element 16.
However, variations of the arrangement of the optical element 16
relative to the LED element 15, and in particular variations to the
distance d, can significantly alter the output beam. A variation of
the distance d may in particular alter the intensity of the output
beam.
FIG. 10a shows a schematic representation of a simple box-shaped
holder 14' for positioning the optical element 16 relative to the
LED element 15. In this comparative example, the holder 14'
comprises on each side a first portion 24a extending straight into
the direction of the optical axis O and a second portion 26
extending from the end of the first portion 24a at right angles up
to the optical element 16.
Assuming a significant CTE mismatch between the material of the
holder 14' and the base plate 12 in the comparative example, a
raised temperature will lead to distortions schematically shown in
FIG. 10b. As illustrated, this will lead to a significant change in
the relative arrangement of the LED element 15 and optical element
16, in particular with regard to the distance between these two
elements.
FIGS. 9a, 9b show a generic embodiment of a holder 14 for
comparison. In the generic embodiment, the holder 14 comprises on
both sides of the optical element 16 a first portion 24a extending
into the direction of the optical axis O and a second portion 24b
extending parallel thereto, but offset in traverse direction. The
first and second holding portions 24a, 24b are connected by a first
connection portion 26a extending at right angles to both the first
and second holding portions 24a, 24b. The second holding portion
24b is connected to the optical element 16 by a second connecting
portion 26b, also arranged at right angles with both the first and
second holding portions 24a, 24b.
As shown in FIG. 10a, the first holding portion 10a extends into
the direction of the optical axis O beyond the optical element 16.
The second holding portion 24b is arranged at a certain distance
from the first holding portion 24a, but parallel thereto. The
second holding portion 24b, the first connecting portion 26a and
the upper part of the first holding portion 24a form a loop-like or
spring structure on both sides of the optical element 16.
In a case of increased temperature and severe CTE mismatch as shown
in FIG. 9b, the holder 14 undergoes significant distortion, but
this does not result in substantial changes in the positioning of
the optical element 16. The angular relationship of the holding
portion 24a, 24b and the connecting portions 26a, 26b may change
and compressive stress in traverse direction may be generated in
the optical element 16, but positioning of the optical element 16
with regard to the optical axis O remains relatively constant. The
spring/loop structure at least partly compensates the deformation
in the first holding portion.
In the first embodiment of a lighting arrangement 10 shown in the
sectional views of FIG. 4, 5, the holder 14 is comprised of plane
wall elements comprising first (outer) holding portions 24a which
extend straight into the direction of the optical axis O and second
(inner) holding portions 24b arranged spaced therefrom in parallel.
As in the generic embodiment of FIG. 9a, 9b, first connecting
portions 26a are arranged in traverse direction to connect the
first and second holding portions 24a, 24b, and second connection
portions 26b are arranged to connect the second holding portions
24b to the optical element 16.
FIG. 7, 8, 11 show alternative embodiments of lighting arrangements
10, which differ from the lighting arrangement 10 according to the
first embodiment by the shape and arrangement of the first and
second holding portions 24a, 24b.
In the second embodiment according to FIG. 7, the first and second
holding portions 24a, 24b are arranged at an angle of e. g.
30.degree.. In the third embodiment according to FIG. 8, the first
and second holding portions 24a, 24b are connected by a curved
portion.
In the fourth embodiment according to FIG. 11, there are further
holding portions 24c, 24d extending in parallel into the direction
of the optical axis O besides the first and second holding portions
24a, 24b. All holding portions 24a-24d are arranged spaced from
each other and are interconnected by perpendicular connecting
portions. The holding portions 24a-24d are of different length,
being shorter the closer they are to the optical element 16. Thus,
a plurality of loop/spring structures is formed, which in the event
of distortion due to CTE mismatch effectively compensates
displacement in the direction of the optical axis O.
For a CTE mismatch between the material of the base plate 12 with
the material of the holder 14 and optical element 16, all of the
described holding structures show an improved behaviour over the
comparative example of FIG. 10a, 10b. Best results have been
obtained with the holder 14 according to the first embodiment.
While the invention has been illustrated and described in detail in
the drawings and forgoing description, such illustration and
description are to be considered illustrative or exemplary and not
restrictive; the invention is not limited to the disclosed
embodiments.
For example, while the above embodiments show a plurality of LEDs
15 in a line and correspondingly aligned optical elements 16,
embodiments with only a single LED or optical element 16, or with
other arrangements such as two-dimensional matrices of LED's and
corresponding optical elements 16 may be provided. While the holder
14 and optical element 16 in the embodiments are provided as one
piece, to be manufactured e.g. by injection moulding, alternative
embodiments are conceivable with separate parts. Also, as
illustrated by the different shapes shown in FIG. 7, 8, the
specific shape of the first and second holding portions 24a, 24b
may vary as long as at least a portion of both extends into the
direction of the optical axis O, even if it is bent, rounded or
inclined. Other variations to the disclosed embodiment can be
understood and effected by those skilled in the art in practicing
the claimed invention, from a study of the drawings, the disclosure
and the appended claims.
In the claims, the word "comprising" does not exclude other
elements, and the indefinite article "a" or "an" does not exclude a
plurality.
The mere fact that certain measures are recited in mutually
different dependent claims or embodiments does not indicate that a
combination of these measures cannot be used to advantage.
Any reference signs in the claims should not be construed as
limiting the scope.
* * * * *